With the clocks going back reminding us we are in autumn, now is the time to be extra vigilant regarding Atypical Myopathy.
Atypical myopathy (AM) is a muscle disease which can be caused when horses eat a toxin found in the seeds, seedlings and leaves of the Sycamore tree.
We tend to see most cases at this time of year due to the leaves and characteristic 'helicopter' seeds coming down, and in spring when seedlings start to come up.
The toxin (hypoglycin A) is produced by Sycamore trees (a member of the Acer family). The toxin has also been found in some other less-common Acer species including the Japanese Maple and the Silver Maple. Importantly the hypoglycin toxin has not been found in the Field Maple or Norway Maple which are considered to be safe. It can be helpful for land owners to identify Sycamore and other Maple trees.
Further information to assist with identification is available from the Woodland Trust and Tree Guide UK.
Horses with this disease develop severe muscle damage. This occurs because the muscles aren’t able to generate enough energy. Muscle damage can lead to a horse becoming weak, reluctant to move or unable to stand. They will often show signs of sweating, distress, reduced appetite and other colic-like signs. Swelling or hardening of the muscles is sometimes visible and they can resent being touched.
What can I do to minimise the risk of my horse developing AM?
• Check fields and tree lines for the presence of sycamore trees. The 'helicopter' seeds can be carried a long way in the wind so regularly inspect pastures for sycamore seeds, leaves and seedling and remove if seen
• Fence off any contaminated areas of pasture and remove horses from the pasture while doing so. If possible, remove stock entirely from the pasture during high risk times of year (autumn & spring)
• Provide extra forage (hay or haylage) as some seeds will remain on the pasture and in spring the seeds germinate rapidly and new seedlings will appear daily. This extra forage reduces the likelihood of the seeds or seedlings being eaten
• Reduce stocking density on a pasture so there is plenty of grass for the horses to eat
• Monitor horses closely after they have been moved from an affected pasture as disease can occur up to four days after exposure
If you think your horse may have this disease, contact your vet immediately.